A micromechanics-based creep damage model for brittle rocks

Abstract

For brittle rocks, the essential non-linear mechanism of material degradation and structure failure can be related to cracking-induced inelastic deformation and damage evolution. This paper is devoted to modelling non-linear time-dependent mechanical behaviour of brittle rocks under compression. A micromechanics-based damage-friction coupling model is developed based on the linear homogenisation method and within the irreversible thermodynamics framework. Firstly, the free energy in the matrix-cracks representative volume is determined, from which are derived the thermodynamic forces associated with the inelastic strains and the damage. Under isotropic assumption, the evolutions of the two internal variables are calculated, respectively, using an associated Coulomb-type friction criterion and a strain energy release rate-based damage criterion. By accounting for subcritical cracking mechanism, the basic model is then extended to describe time-dependent creep deformation and applied to simulate triaxial compression tests and triaxial creep tests on granite. Comparisons of numerical predictions with experimental data are performed to show the predictive capacity and the advantage of the proposed model.